A variety of orthopedic devices, including bone reduction and distraction devices, are known in the art. Reduction and distraction devices (commonly referred to as reducers and distractors), are used to gradually adjust the relative orientation and spacing of the bone parts on opposing sides of a bone repair site. As used herein, “bone repair site” refers to any bone region which is bounded on opposing sides by relatively healthy bone regions to which orthopedic devices can be secured, such as an osteotomy (cutting of a bone) or a fracture.
Reducers and distractors typically consist of transcutaneous pins or screws secured in the bone on either side of the bone repair site together with a mechanism which allows controlled incremental adjustment of the distance between parts of the device on opposing sides of the bone repair site. Typically, distractors are used to perform distraction osteogenesis (the formation of bone). This procedure was perfected by the Russian orthopedic doctor, Gavriel Ilizarov. A typical procedure of this type involves at most an osteotomy completely separating the bone into two segments, or at least an incision of the cortical portion of the bone. Then, the bone segments on either side of the osteotomy (or the medullary or cancellous portion of the bone on either side of the incision) may be expanded. This gradual separation allows new bone to form in the osteotomy void. The distraction phase is followed by a consolidation phase, during which the distractor is held fixed, and the new bone growth gains strength. Following the consolidation phase, the distractor is removed from the patient.
One area in which distraction techniques are used is in treating patients diagnosed with maxillary hypoplasia (underdevelopment of the maxilla, or upper jawbone). One particular patient population with this condition is cleft-lip and -palate patients. The key reason for utilizing maxillary distraction to treat these patients is in the ability to successfully overcome the substantial soft tissue forces found in the maxillary region of these patients. Cleft-lip and -palate patients usually undergo surgery to correct their soft tissue deformities in early infancy. These procedures involve a great deal of soft tissue dissection, and leave the patient with significant scar tissue surrounding their maxillary region. As a result of the reduced elasticity of the scar tissue as compared to regular soft tissue, the maxilla is very often restricted from normal growth and can be very difficult to advance using conventional orthognathic surgery (surgery relating to treatment of the malpositioning of bones of the jaw). Maxillary distraction thus allows the tensile forces of the scar tissue to be overcome, and a greater advancement distance to be achieved, with a clinically supported expectation of a lesser degree of relapse (undesired movement of maxilla back towards its original position after treatment is finished).
An additional patient population that can take advantage of maxillary distraction is non-cleft palate patients having an A-P (Anterior-Posterior) maxillary deficiency of large magnitude. Typically, orthognathic procedures involving maxillary advancements are limited in the magnitude of the advancement of the maxilla due to the elastic properties of the surrounding soft tissues. Also, the larger advancements are more likely to require a bone graft to the site to ensure the long-term stability of the advancement. Using distraction for maxillary advancements can eliminate the magnitude limitations as well as the need for grafting for these patients.
Another benefit of performing maxillary distraction on cleft-lip and -palate patients is the ability to treat the maxillary hypoplastic patients at a younger age than with conventional orthognathic surgery. Early treatment of skeletal deformities has been gaining in popularity among craniofacial surgeons as a means of minimizing the negative psychosocial impact that craniofacial deformities have on children. Also, some surgeons believe that early correction of skeletal deformities can reduce the residual impact on surrounding tissues and structures, thus improving the overall result for the patient. See, for example, Steven Cohen, M.D., F.A.C.S., “Midface Distraction,” Perspectives in Plastic Surgery, Vol. 11, No. 1.
However, the only available devices that can be used for maxillary distraction have external “halo-style” fixators that attach to the skull and to the maxilla by way of surgical wires affixed to an intra-oral appliance. One such known halo system is the KLS-Martin RED (Rigid External Distraction) system. Such a high profile external device is unsightly, and the psychosocial effects of wearing an external device is a major concern, especially with younger patients. An external device is also more subject to bumps and snags than one which is completely located within a patient's body. Accordingly, there is a need in the art to provide a device that can be used intra-orally to reliably perform distraction or reduction of the maxilla.
Furthermore, the known external fixators involve a large number of component parts and accordingly are complicated to install and adjust. Accordingly, there is a need in the art to provide a device that can be used to perform distraction or reduction of the maxilla that has a relatively low part count, and is simple both to install and adjust. Furthermore, there is a need for a distractor which occupies as little space as possible in the patient's mouth, even when the device is extended to its full length. In addition, there is a need to provide the installing surgeon with the flexibility to choose from multiple actuator lengths and footplate sizes, even after installation of the device has begun. Finally, there is a need to provide an intra-oral distractor whose alignment in the patient's mouth may be easily verified.